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Endangered snuffbox mussels were rescued near a dam removal project in Miami County, Ohio.  Photo by JenniferFinfera/USFWS.

Endangered snuffbox mussels were rescued near a dam removal project in Miami County, Ohio. Photo by Jennifer Finfera/USFWS.

Endangered Mussels Rescued at Ohio Dam Removal Site

Working with partners, the U.S. Fish and Wildlife Service’s Ohio Field Office helped rescue and relocate endangered sheepnose mussels in west central Ohio before removal of a dam on the Stillwater River. ¬†Since 2010, the U.S. Fish and Wildlife Service has been part of a collaborative effort to remove the West Milton Dam on the Stillwater River, a state scenic river in Miami County, Ohio.

Built in 1918 to generate electricity and later used to provide drinking water, the 13-foot-tall West Milton Dam spanned 305 feet and impounded more than 2 miles of the Stillwater River. Almost a century after construction, the aging dam did not meet current safety standards, and costs to upgrade it were prohibitive. A dam removal feasibility study was funded by the Service through the Fish Habitat Partnership, and the Ohio Environmental Protection Agency Water Resource Restoration Sponsor Program provided funding to remove the dam.

In August 2011 before the dam was removed, a mussel survey found a single fresh-dead snuffbox mussel (Epioblasma triquetra) at the upstream end of the impounded stream. The rayed bean (Villosa fabalis), another freshwater mussel, had been recorded from locations both upstream and downstream of the dam. Both the snuffbox and rayed bean were listed as endangered species on March 15, 2012.

In the fall of 2013, as efforts began to move forward on dam removal, the Columbus Field office worked with the Army Corps of Engineers and its consultants to discuss the project timeline and measures to avoidance and minimize impacts to the mussels from dam removal activities. In spring of 2014 the Columbus Ohio Field and the Corps initiated formal consultation so that an incidental take statement for impacts to the snuffbox and rayed bean could be issued. Recommendations were made and implemented to avoid impacts to other federally listed species whose ranges covered the project area.

To avoid and minimize impacts to mussels and other aquatic organisms, dam removal began in late October 20104 during low-water levels. The dam was notched incrementally so that water upstream of the dam would be drawn down slowly and sediment releases would be reduced. The timed release of water enabled partners to thoroughly search exposed habitat for mussels before the next drop in water level occurred.

Mussel rescue work spanned two weeks. Partners, including the Columbus Field Office, the Service private lands office, and the Ohio River Foundation, used rakes and shovels to dig into the exposed substrate as the water level dropped to retrieve mussels that had burrowed into the substrate. Mussel rescuers reached into chilly water to collect mussels before the mussels were exposed by falling water levels. In shallow riffles and gravel bars biologists excavated the substrate with their hands and feet to look for the mollusks. Mudflats were also examined for mussels trapped in sediment.

Among the wide diversity of species and ages collected, rescuers were surprised to find multiple live snuffbox individuals near the upstream end of the impounded area. All rescued mussels were relocated to suitable habitat that would not be exposed once the dam was completely removed. On days when the water was cold, mussels were hand placed in the substrate as these cold-blooded individuals move too slowly to bury themselves when the water is cold.

Removal of the dam is now complete. Work continues on construction of two gravel riffles to stabilize the new channel, and native vegetation will be planted in the spring to restore construction access paths. Increased flows resulting from dam removal will provide suitable habitat for multiple mussel species, including the rayed bean and snuffbox which prefer higher stream flows. In addition, removal of the dam will connect fish and mussel communities upstream and downstream of the former dam. In several years, a follow-up survey will be conducted to determine the status of the relocated mussels.

Removal of the dam has restored over 30 miles of free flowing quality riverine habitat. The snuffbox population in this area is expected to thrive under the improved habitat conditions!

By Jennifer Finfera
Columbus Ohio Ecological Services Field Office

 

Last updated: March 5, 2015